Pen cap



FIG. 1 is a perspective view of the pen cap showing my new design;

FIG. 2 is a front view of the pen cap;

FIG. 3 is a side view of the pen cap;

FIG. 4 is a top view of the pen cap; and,

FIG. 5 is a bottom view of the pen cap. 

The ornamental design for a pen cap, as shown and described. 